When Urban Security Cameras Actually Save Lives

Taxi driver homicide rates are three times lower in cities with in-car cameras.

More and more cities are turning to surveillance cameras as a cost-effective tool for public safety, sometimes with the specific goal of fighting terrorism, but they're still pretty far from universally accepted. Many people object to cameras on the grounds of public safety; others simply don't believe they actually prevent crimes. There is one place where urban security cameras do seem to save lives, however: taxi cabs.

That's the conclusion reached by a new study of driver homicides in 26 U.S. cities, just released in the American Journal of Preventive Medicine [PDF].

Driving a taxi has long been one of the riskiest professions in terms of personal safety, what with attention directed on the road and all that loose cash laying around. In the early 1990s, a number of cities implemented bullet-resistant partitions to disrupt potential attacks on cabbies. More recently, some cities (or, in some cases, some companies) have insisted that taxis install security cameras for their protection.

While a few studies have found some safety benefits from these measures, most of that work focused on short-term gains. The new research, led by Cammie K. Chaumont Menéndez of the National Institute for Occupational Safety and Health, analyzed driver homicide rates over a 15-year period from 1996 to 2010. Chaumont Menéndez and colleagues split the 26 cities into three groups: camera cities, partition cities, and control cities that had taken no cabbie precautions.

The researchers identified at least 216 taxi driver murders during the study period through newspaper searchers, but very few of them occurred in cities that had installed in-cab security cameras. In fact, the driver homicide rate in these eight cities was about seven times lower after installation than it had been before. Additionally, the homicide rate in camera cities was more than three times lower than the rate in control cities where no cameras were used — even after the data were adjusted for overall city murder rates.

Surprisingly, partitions provided no measurable safety benefit at all. The researchers found no statistical difference in driver homicide rates in cities that had implemented partitions compared to those that had implemented no security precaution.

Chaumont Menéndez and colleagues offer some pretty basic explanations for why security cameras were such an effective deterrent. They believe would-be assailants were discouraged by window decals advertising the presence of the cameras, and that city mandates on camera maintenance served to keep the equipment in working order. Indeed, city governance played a huge role here: while a handful of homicides occurred in "camera" cities after installation, none happened in cities with official camera mandates.

Instead, these murders took place in cities where cab companies, not municipal governments, oversaw the programs.

The work suggests that all cities concerned about taxi driver safety should consider a shift toward camera installation. On a broader level, it also points to the potential social benefits of public surveillance. There is certainly something unsettling about the idea of being watched all the time, but there can be something comforting about it, too.